The present invention generally relates to the field of carburetors for internal combustion engines and, more particularly, to carburetors that utilize priming systems to aid in engine starting.
Internal combustion engines are used in a variety of applications, such as for outdoor power equipment which includes, for example, lawn mowers and other lawn and garden equipment, snow blowers, generators, pumps, and the like. Such engines generally include a carburetor wherein fuel received from a fuel source is mixed with air and supplied to a combustion chamber for ignition. To aid in starting such engines, it is generally desirable to provide fuel directly into the carburetor throat prior to engine start-up. This may be accomplished through the use of many different known priming systems.
One such type of priming system includes a primer bulb which, when depressed, displaces a volume of air above the fuel level in a fuel well, wherein the pressurized air urges fuel from the fuel well through a fuel nozzle and into an intake passageway or throat of the carburetor where the fuel is mixed with air and then drawn into the intake manifold of the engine to aid in engine start-up.
A common problem associated with priming systems using a fuel well is that after a priming operation, fuel is typically only slowly replaced in the fuel well. Therefore, if the operator attempts to prime the engine several times in rapid succession, no fuel or not enough fuel is present in the fuel well after the first priming operation, so that the only effective priming operation is the first such operation.
Another common problem associated with priming systems using a fuel well is that each priming charge is limited to the volume of the fuel well, which is typically quite small compared to the fuel bowl where the operating fuel is located, and often not sufficient to efficiently aid in engine start-up.
Another common problem associated with priming systems using a fuel well is that a portion of the pressurized air used to urge fuel from the fuel well through a fuel nozzle and into an intake passageway or throat of the carburetor may escape through an internal venting passageway, thereby decreasing the effectiveness of the priming system. Thus, in order to reduce the loss of the pressurized air, it is known to provide the opening of the venting passageway with a small diameter. A drawback of this type of arrangement is that it is difficult to calibrate the carburetor because of the vacuum created on account of the small diameter vent.
Another common problem associated with priming systems using a fuel well relates to the widely accepted principle that for those carburetors that utilize a fuel metering orifice to regulate the passage of fuel from the fuel bowl to the fuel well, the internal vent for the fuel well must be proportionately sized to the fuel metering orifice to achieve acceptable calibration results. It is desirable to make the fuel metering orifice as large as possible to enhance priming operations by delivering as much fuel as possible to the carburetor throat so that during starting, heavy load conditions and acceleration, a sufficient amount of fuel is delivered to the intake passageway of the carburetor, to ensure efficient starting and continuous, smooth operation of the engine. However, providing a large fuel metering orifice generally results in also providing a large fuel well vent and, as previously noted, a large fuel well vent generally results in a significant portion of the displaced pressurized air escaping through the fuel well vent during priming. Although restricted fuel jetting solves the problem of having a large fuel well vent, restricted fuel jetting detrimentally affects engine efficiency in terms of engine starting and engine operating performance.
The present invention overcomes the above-noted problems and other problems of the prior art and includes the above-noted features and other features by providing a carburetor for use with an internal combustion engine, wherein a passageway extends between a variable volume chamber of a primer bulb and a fuel well. The passageway is separate and distinct from the fuel well. The passageway is situated such that the outlet of the passageway into the fuel well is below the priming fuel level which at least partially extends into the passageway. The displacement of a volume of air from the primer bulb through the passageway and into the fuel well results in a squirting of a quantity of fuel into a fuel nozzle of the carburetor to provide a priming charge to the carburetor intake passageway. Because the outlet of the passageway into the fuel well is below the priming fuel level, no significant portion of the displaced pressurized air can be lost through a venting aperture. Thus, the size of a fuel metering orifice used to regulate the passage of fuel from a fuel bowl to the fuel well is not limited by an acceptable size for a venting aperture or passageway, as is the case in known prior priming systems. Therefore, the size of the fuel metering orifice can be advantageously increased for improved priming responsiveness and to also better handle heavy loads and acceleration, without concern for the resulting proportionately sized fuel well vent.
Accordingly, the present invention provides a priming system for an engine carburetor that improves the starting efficiency of the engine, enhances calibration consistency, and improves performance characteristics of the engine during operation.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.